For the past number of years I have studied diagnostic screening and psychiatric diagnostic methods in children and adolescents. This work has included creation of DSM-IV compatible versions of the Diagnostic Interview Schedule for Children (DISC-IV) and the DISC Predictive Scales (DPS) as well as investigating the science of self-report, and understanding the mechanisms behind unreliability of symptom reports. I have researched the value of computerized self-assessment, both as a more sensitive method of gathering certain types of information and as a uniquely useful tool for public health psychiatry and epidemiological research. In addition to existing work on experimental approaches aimed at improving the reliability of diagnostic assessment and an ongoing program of development and psychometric testing of diagnostic screening instruments, this Independent Scientist Award will enable me to answer important questions regarding the validity of measurement of child psychopathology. Three areas will be studied: 1. Diagnosis in young children: Despite strong clinical and epidemiological needs, the methods and techniques for determining accurate diagnostic status are lacking. Via a multi-modal longitudinal validity study of 120 pre-school children, derived from a pediatric primary care population, it is intended to: Study the necessary symptom and contextual information for diagnosis; Develop the diagnostic methods and protocols required for accurate assessment; Assess the predictive validity of DSM-IV and alternative diagnostic algorithms; and Examine the relative value of information from different informants and the optimal methods for its synthesis. 2. Audio-CASI: Computerized self-interviewing with audio (A-CAST) has been shown to yield increased reporting of sensitive symptoms. The validity of these reports will be examined by comparing reports of drug/alcohol usage to objective biological assays (hair and urinalysis) in a sample of 2,000 high-risk youth. 3. Discrepant reports: Unreliability in repeated measures is a major problem to both epidemiological and treatment researchers. The predictive validity of discrepant reports will be assessed in a sample of 300 community adolescents and their parents who previously had participated in a test-retest study.